Osteoarthritis is a chronic joint disease characterized by the destruction (wear) of the articular joint cartilages. It can be primary or secondary to joint deformities affecting the hip and the knee. Hip (coxarthrosis) and knee osteoarthritis (gonarthrosis) are the most common forms of osteoarthritis, and can eventually cause permanent or secondary impairments, even though this functional prognosis has significantly changed with replacement surgery (artificial joints).

What is osteoarthritis?

Osteoarthritis may be primary or secondary. It is primary, when no underlying cause or joint deformity can be found and secondary, when it is the result of a congenital or acquired joint deformity (joint fractures, severe ligament injuries, or vascular lesions following an accident). Osteoarthritis may affect a single joint, as in secondary osteoarthritis, or multiple joints. In the case of the latter, it is referred to as osteoarthritic disease.

Current research has not yet identified the internal mechanism responsible for the disease progression, which is why anti-arthritic, disease-modifying treatments are so rare. Although it is a degenerative process, osteoarthritis should not be confused with aging—although aging increases the incidence of these diseases; there is always a predisposition of a biomechanical factor or a favorable genetic background.

Osteoarthritis may occur in particular settings, such as in calcium pyrophosphate dihydrate deposition disease (CPPD) or chondrocalcinosis. This inflammatory condition is similar to rheumatoid arthritis, but the onset occurs later in life (after 50 years of age). Radiographs of the affected areas indicate the presence of crystal deposits covering the joint cartilage. The most frequently affected joints are in the wrist, fingers, shoulder, hip, and knee.

Hip osteoarthtitis or coxarthrosis

Primary coxarthrosis

Clinical manifestations

The presentation can be unilateral, but most often bilateral in cases of polyarticular arthritis. The onset of signs and symptoms usually occurs after 40 or 50 years of age and their progression is slow and rarely symmetrical. The diagnoses can be confirmed in clinical settings: walking, going up and down stairs, crouching, etc. aggravates biomechanical pain, but resting in a lying position decreases the pain. Coxarthrosis is traditionally said to be progressive; in fact, it often manifests in outbreaks lasting for a few weeks or months, during this time the pain may be severe. Besides these painful outbreaks, coxarthrosis is usually well tolerated.

Figure 1

Osteophytes (bony spurs) indicate that the joint is affected.

Narrowing of the joint space between the femur and pelvis (acetabulum) is a sign of cartilage loss (invisible on the radiograph).

On examination, the person may present with an antalgic gait (short stance phase of the affected limb), or an abnormal posture (most frequently in flexion/external rotation). Range of motion is limited, especially in extension, abduction and internal rotation. Periarticular muscle contractures may also be present.

The diagnosis is further validated through radiographic examination (figure 1B): joint space narrowing (space between the bones of a joint) indicates cartilage loss; formation of osteophytes (bony spurs), and even subchondral cysts (cavities) on the acetabulum and femoral head (2) indicate significant joint pain.

Progression under treatment

The disease evolves over several years, sometimes over more than 10 to 20 years, and requires the use of analgesic or anti-inflammatory medications during outbreaks. Rehabilitation helps to maintain proper active joint motion and muscle strength. Coxarthrosis is more easily tolerated in individuals with strong hip muscles. In the most painful forms, therapy pool rehabilitation and climate therapy are often successful in reducing the pain. Limiting the ability to walk long distances, difficulties in the performance of daily activities, stiffness of the hip due to limited flexion and external rotation, and the presence of severe pain awakening the individual at night may require a determined surgical intervention: arthroplasty or total hip replacement. This reliable type of surgery has been practiced for little over 30 years and has dramatically transformed the overall performance and life of individuals with coxarthrosis.

Secondary Coxarthrosis

Coxarthrosis secondary to hip deformities

Secondary coxarthrosis occurs in congenital hip deformities in the majority of cases. In congenital dislocation (figure 2C) (in severe forms); the femoral head protrudes out of the cavity of the acetabulum where it is usually located. In simple dysplasia (in minor forms) the upper part of the acetabulum ('roof') does not sufficiently cover the femoral head (figure 2B). In this form of coxarthrosis, the first onset of signs and symptoms occurs before age 30. The progression is faster than in the primary form. Yet, it should be clarified that systematic screening of hip deformities and suggested treatments have uniquely reduced the frequency of these forms. This condition is particularly observed in Britain.

Therapy: during adulthood, in order to prevent the progression of the disease into arthritis and to mitigate the effects of the disease, surgical intervention to correct hip dysplasia may be a valid option. If the patient is increasingly invalidated by the disease progression, the most commonly selected surgical intervention may be total hip arthroplasty (prosthesis).

Figure 2

Normal hip

Dysplasia: the roof of the acetabulum does not sufficiently cover the femoral head

Dislocation: displacement of the femoral head

Other causes of secondary coxarthrosis

The less frequent forms of coxarthrosis include: arthritis caused by calcium pyrophosphate dihydrate disease (chondrocalcinosis), osteoarthritis, post-traumatic arthritis (following a fracture or dislocation), arthritis following necrosis of the femoral head following a traumatic injury (the femoral head degenerates developing deformities). These forms of coxarthrosis may evolve rapidly, requiring total hip replacement surgery. These forms with rapid progression are called rapidly destructive hip diseases (RDHD).

Knee arthritis or gonarthrosis

As common as coxarthrosis, gonarthrosis can also be distinguished as primary and secondary conditions. However, considering the anatomical structure of the knee, gonarthrosis may affect either one or its three functional compartments.

Primary gonarthrosis

Primary gonarthrosis most frequently affects the three joint compartments. It is bilaterally, but not necessarily symmetrical (figure 3).

Figure 3

Circumstances of detection: painful outbreaks, may be accompanied by effusion, awkward gait, difficulty in the performance of daily activities, as well as ascending and descending stairs. The pain is typically relieved by resting in the prone, and often exacerbated by prolonged sitting. It progresses in the form of painful and pseudo-inflammatory outbreaks over several weeks or months. The arthritis may be well tolerated besides these outbreaks.

Physical examination often reveals antalgic gait or significant gait disturbance due to joint stiffness, which is confirmed during the examination, showing a flexion contracture (the loss of extension is detrimental to the function and stability of the knee joint). The range of flexion available at the knee is also limited. The associated effusion in the knee joint may require therapeutic tapping/puncture procedures. Significant pain in the entire capsule of the knee joint is also reported. Atrophy (muscle wasting) of the thigh muscle is typically associated with this condition. Radiographic examination is used to confirm the diagnosis.

Therapy: Analgesic and anti-inflammatory medications are taken during periods of relapses. Intra-articular cortisone injections are often successful in reducing the pain for several weeks/months, and are easier to perform in the knee than in the hip.

Rehabilitation is essential to preserve the joint mobility, to counterbalance flexion deformity of the knee, and above all, to maintain the strength of peri-articular muscles, which assists to improve the joint stability. When properly rehabilitated, knee arthritis becomes easier to tolerate, which may allow postponing the surgery.

The progression typically occurs over one or two decades. When it comes to the point of hindering knee function and generating continuous pain, total knee arthroplasty (prosthesis) is performed.

Secondary gonarthrosis

Frequent and occurring along with dysplasia of the knee—especially on the patellar joint— secondary gonarthrosis is often the result of untreated fractures, sprains, and meniscus injuries.

In these forms of gonarthrosis, the affected area may be located in a single compartment (affecting only one of the three compartments of the knee: fig. 3). These forms are either called patellofemoral arthritis (the most tolerated form), medial femorotibial arthritis associated with genu varus (also called 'bow legs' or 'bandy legs'), which is the less tolerated form, or lateral femorotibial arthritis associated with genu valgum (also called 'knock-knees'). These forms of arthritis affecting a single knee compartment and usually respond well to rehabilitation. When they are very hard to tolerate and invalidating for the patient, single-compartment knee prosthesis may be suggested. Prior to any other action and in the case of severe deformities, corrective osteotomies can be performed in order to gain a few more years of mobility.

There are other forms of gonarthrosis: the arthritis caused by the calcium pyrophosphate dihydrate deposition disease evolves by pseudo-inflammatory outbreaks and may respond well to injections. Osteonecrosis, of the medial condyle are fairly specific. It requires the patient to reduce the load on his affected knee during the stance phase by walking with bilateral crutches for several weeks. Alternatively, he or she may also choose to get a single-compartment prosthesis.